Electrolytic cell



March 14, 1939. G. MESSNER 2,150,775

' ELECTROLYTIC CELL Filed Sept. 15, 19:56

Patented Mar. 14, 1939 UNITED STATES PATENT OFFICE Farbenindustrie Aktiengesellschaft,

Frankfort-on-the-Main, Germany Application September 15, 1936, Serial No. 100,798

' In Germany October 4, 1935 I 4 Claims. The present invention relates to improvement in cells for the electrolysis of aqueous saline so-' to keeping the bath voltage as low as possible, it

isdesirable thatthe distance between the electrodes and consequently also the distance of the diaphragm from the surface of the mercury cathode, should be reduced as far as possible. At the same time however, the diaphragm must be prevented from coming into contact with the mercury, on account of the violent decomposition of the amalgam, and the risk of destroying the diaphragm which would otherwise ensue.

- When constructing ordinary cells having hori'-' zontal electrodes, in which the mercury cathode is disposed at the bottom of the cell, great difii- .culties have been encountered in finding a. suitable diaphragm. 'Ii ns, flexible diaphragms stretched across the cell and consisting for example of a fabric support coatedwith a paste of barytes and asbestos fibre or of any other flexible material such as asbestos paper, have the disadvantage of sagging, thus rendering it impossible to maintain the desired spacing between the diaphragm and the mercury cathode. On the other hand, if the diaphragm be supported at various points inside the cell so as to prevent sagging, the arrangement of supports on the underside of the diaphragm necessarily involves an increase in the distance between the electrodes. It has therefore been found very diflicult and expensive to produce practical diaphragms which are capable of complying with the mechanical and electrochemical requirements arising in the construction of 'such cells.

The present invention aims at providing an apparatus for the electrolysis i aqueous solutions of sodium sulphate by the amalgam process, which has horizontally disposed electrodes and diaphragm which is free from the foregoing drawbacks, by virtue of the anode being located below,

and the mercury cathode above, the diaphragm, '0 the mercury being separated from the diaphragm by allowing it to flow in suitably designed channels of electrically insulating and chemically resistant material, superposed directly on the dia- Phras I with a view to lowering the bath voltage the anode is preferably in sheet form and preferably also of corrugated cross section, the channels containing the mercury being located in the troughs of the corrugations. This arrangement enables the diaphragm to be laid directly on and to fol- 5 low the curvatureoi the undulating anode, the corrugations of which are preferably sinusoidal in form. The anode is perforated to enable the anolyte'to pass therethrough into a collecting chamber beneath it.

In order more clearly to understand the invention, reference is made to the accompanying drawing which illustratesdiagrammatically and by way of example. one embodiment thereof, and

in which: 1s

Fig. 1 is a top plan view; and

Fig. 2 is a cross section along the line o-b of Fig. l:

In said drawing, I denotes a vat having a bot tom outlet 2 for the anode liquor. Horizontally disposed in the lower part of said vat I is a perforated lead anode 3. .A diaphragm 4 of asbestos paper is laid directly on the anode and is in turn covered by a slotted framework comprising a series of troughs 5 which framework is stamped out of corrugated sheet iron and is covered with a 2 mm. layer of hard rubber. In the embodiment shown, the space between the middle of adjacent troughs is 60 mm. Thetroughs oi the corrugations serve as channels for the mercury forming the cathode which "is admitted at 6 and issues, in

the form of amalgamat I. The electrolyte consisting of sodium sulphate solution is denoted by 8. The electrolysis of a neutral solution of sodium sulphate (density 1.32) using a current density of 2700 amps. per sq. metre at the cathode and a voltage of 6.9, furnishes an anode liquor containing 125 grms. oi H2804 per litre, the current yield being 97%.

The following advantages are obtained with the hereindescrlbed apparatus:

(1) In contrast to the known type of con-.

struction, the mercury surface of the cathode is freely accessible.

(2) The electrolyte flows, under-its own hydrostatic pressure, from above downwards and therefore does not need to be drawn oil as heretofore. (3) The whole surface of the diaphragm lies in the anode and is therefore practically freed from mechanical stressing, so that mechanically so weak materials may be employed in its construc: tion.

I claim: 1. A cell for the electrolysis of aqueous saline solutions, by the malgam process, comprising a container, a substantially horizontally disposed diaphragm, an anode disposed below said diaphragm, electrically insulating and chemically resistant means for conducting a liquid, disposed above said diaphragm, and mercury serving as a cathode contained in said means, said means being so disposed and so constructed as to allow. passage of the electric current between said mercury cathode and said anode;

2. A cell for the electrolysis of aqueous saline solutions, by the amalgam process, comprising a container, a substantially horizontally disposed diaphragm, an anode disposed below said diaphragm, at least one substantially horizontally disposed trough-shaped channel of electrically insulating and chemically resistant material superposed directly on the diaphragm and out of contact with the walls of said container along its length, and mercury serving as a cathode contained in said trough-shaped channel.

3. A cell for the electrolysis of aqueous saline solutions, by the amalgam process, comprising a container, a substantially horizontally disposed corrugated anode provided with perforations, superposed thereon a diaphragm or pliable material, a plurality of trough-shaped channels of electrically insulating and chemically resistant material disposed in and resting on the troughs formed by the corrugations of said diaphragm,

and mercury serving as a cathode contained in said trough-shaped channels.

4. A cell for the electrolysis of aqueous saline solutions, by the amalgam process, comprising a container, a substantially horizontally disposed corrugated anode provided with perforations, superposed thereon a diaphragm oi pliable material, a plurality of trough-shaped channels of corrugated sheet iron stamped to shape and provided with 'a coating of hard rubber disposed in and resting on the troughs formed by the corruas a cathode contained in said trough-shaped gations of said diaphragms', and mercury serving\2 channels. 5

, GEORG MESSNER. 

